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The hole transport materials that interact with the indium tin oxide (ITO) surface can be processed into monomolecular layers (MLs), which often exhibit different surface and electronic properties than their thin‐film counterparts. Herein, it is found that poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA) films (R‐PTAA) can be easily processed into ML (M‐PTAA) due to the van der Waals interaction between ITO and PTAA. However, compared with R‐PTAA, the work function (WF) and conductivity of M‐PTAA are simultaneously reduced by the charge transfer at the ITO/PTAA interface. To address this issue, a modified monomolecular layer strategy (m‐MLS) is developed, where a small amount of 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) is introduced to enhance the interaction force between ITO and PTAA. PTAA treated by m‐MLS (F‐PTAA) has a hydrophilic physical surface, closely matching electronic energy level with the perovskite layer and smaller bulk resistance. As a result, the efficiency and reproducibility of perovskite solar cells (PSCs) are substantially improved. PSCs based on F‐PTAA demonstrated the highest power conversion efficiency (PCE) of 19.7% with a fill factor of over 80%. This study inspires the development of novel interface modification materials, and provides a simple and convenient direction for the fabrication of high‐performance and reproducible inverted PSCs with high fill factors. [ABSTRACT FROM AUTHOR]

Excess PbI 2 can improve the efficiency of perovskite solar cells (PSCs). However, it usually leads to poor cell stability due to the chemically active nature of PbI 2. Improving the stability of PbI 2 -rich perovskite solar cells without scarifying the efficiency remains challenging. In this work, it is found that the non-uniform and multiple nucleation of perovskite induces crystallographic disorders at grain boundaries (GBs) of PbI 2 -rich perovskite. These disorders working as the n-type shallow dopant reduces the energy barrier for photogenerated electrons to reach GBs, triggering the decomposition of excess PbI 2 there. Therefore, the instability of PbI 2 -rich PSCs is related with the remote coupling of excess PbI 2 with the disorders at GBs. In light of this finding, we introduced a small amount (0.5 mol%) of CdI 2 into precursor solution to optimize the crystallization of PbI 2 -rich perovskite, and finally achieved a trade-off between efficiency and stability in PbI 2 -rich PSCs. The optimized PSCs with 10 mol% excess PbI 2 (PC-Device) achieved a champion efficiency of 24.26% at the bandgap 1.55 eV with robust stability. PC-Devices maintain more than 90% of the initial efficiency after being stressed under UV light in ambient with a relative humidity of 50% for 500 h, and 70% under heat at 85˚C for 400 h, both of which are far superior to the pristine PbI 2 -rich solar cells. [Display omitted] • The instability of PbI 2 -rich PSCs is related to the disorders at GBs of perovskite. • A small amount of CdI 2 is introduced to restrain the disorders at GBs of perovskite with excess PbI 2. • The stability of PbI 2 -rich PSCs is promoted greatly with the assist of CdI 2. • High efficiency (24.26%) and V oc (1.18 V) are achieved for FAMA mixed PSCs. [ABSTRACT FROM AUTHOR]

The role of MA in FAMA mixed perovskite remains far from being fully understood, due to the intricate chemical evolutions in the precursor solutions. Adjusting the content of MA in FAMA mixed perovskite arbitrarily remains a great challenge. This study elucidates a synergistic effect between H+ and I− oxidation which helps to reduce the content of MA in FA‐dominated perovskite. Briefly, excessive H+ boosts the balanced and rapid assembly of MA and FA components in FA‐dominated perovskite and hampers unfavorable chemical evolution induced by nucleophilic reaction between MA and FA in the precursor solution, while I− oxidation accelerates the in situ crystallization of perovskite. Leveraging this synergistic effect, centimeter‐scaled FAxMA(1‐x)PbI3 single crystals with arbitrarily adjustable values of x are successfully fabricated. In addition, peroxyacetic acid is introduced as the additive, enabling the blade‐coated FA0.9MA0.1PbI3 perovskite solar cells (PSCs) to achieve an impressive efficiency of 23.7%. The efficiency achieved here is among the highest values for blade‐coated PSCs with FA content exceeding 90% so far. The optimized solution developed in this study achieved exceptional stability, allowing it to be stored under air conditions for over 2 months without significant degradation in cell efficiency. This outcome satisfies the requirements for commercialization. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have developed rapidly in the past few years. However, highly efficient PSCs prepared in ambient air have remained intractable, since the crystallization and film morphology of perovskite are highly sensitive to moisture. Here, a thermal radiated hot‐cast method (THCM) to prepare high quality perovskite films in ambient air is introduced. The proposed THCM not only eliminates the temperature gradient across the perovskite film, but also forms a significantly reduced and constant relative humidity field at the local space above the substrate (ca. 6%); these conditions result in a smooth, compact, oriented perovskite film with largely reduced grain boundaries. THCM is a universal protocol, based on the application to the devices with both inverted and regular architectures, and it enables improved J–V performance with largely reduced hysteresis. The champion power conversion efficiencies of 17.2% for inverted and 19.1% for regular devices are achieved by THCM. These are comparable to the top efficiencies of fully air‐processed PSCs, demonstrating that THCM is a promising protocol for commercialization of PSCs in the near future. [ABSTRACT FROM AUTHOR]

In this paper, inverted perovskite solar cells (PSCs) employing a novel polymer‐assisted small molecule layer as hole transport layer (HTL) are reported and the effect of mixed HTL on the device performance is investigated. It is the first time that the small molecule HTL is doped with a polymer HTL. The introduction of appropriate content of polymer into the small molecule layer will lead to a much smoother surface for the mixed HTL and largely reduced charge recombination, and most importantly, the energy level alignment is more matched with that of the perovskite via optimization of the doping content. Therefore, the hole transfer property is largely improved for the perovskite/mixed HTL composites. After the optimization of the polymer content in the mixed HTLs, an average power conversion efficiency (PCE) of 19.03 ± 0.53% is achieved, and the champion device exhibits a PCE of >21%. This work provides an effective strategy for the development of highly efficient inverted PSCs based on small molecule HTLs. The hole extraction property of the hole transport layer based on TAPC small molecule via polymer assistance is largely improved. The average power conversion efficiency is enhanced from 17.66 ± 0.52% to 19.03 ± 0.53%, and the champion efficiency reaches 21.01%. [ABSTRACT FROM AUTHOR]

[Display omitted] The p-i heterojunction imbedded underneath the perovskite layer plays a vital role in determining the efficiency and stability of inverted perovskite solar cells (PSCs). We found that poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) suffers from the severely chain entanglement resulting in poor contact with perovskite. In this work, PTAA layer was treated by poly[(2,6-(4,8-bis(5-(2-ethylhexylthio)-4-fluorothiophen-2-yl)-benzo[1,2-b:4,5-b′] dithiophene))- alt -(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl) benzo[1′,2′-c:4′,5′-c′] dithiophene-4,8-dione)] (PBDB- T -SF) diluted solution in chlorobenzene. PBDB- T -SF, which contains dual carbonyl groups in its backbones and suitable electronic levels, can spontaneously fill the voids in chlorobenzene-washed PTAA (nano-PTAA). This not only promotes the work function of the substrate but also strengthens the coherence between perovskite and the substrate. Blade coated PSC (0.09 cm2) containing PBDB- T -SF (s-PSCs) realized a power conversion efficiency (PCE) of 21.83 %. After aging for more than 2000 h, s-PSCs maintains 88 % of the initial efficiency which is only 59 % for the control devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tetrabutylammonium chloride (TBAC) monomolecular layer produces strong dipole moment on the surface of perovskite. • TBAC surface treatment enables a champion efficiency of 23.5% with negligible hysteresis for final solar cells. • TBAC surface treatment sustains even under high temperature harsh conditions. Surface "molecule treatment" has been widely used to promote the performance of perovskite solar cells (PSCs). However, the low tolerance in thickness and difficulty in energy level matching restrict its applications in large-scale manufactures in the future. In this work, a mono-molecule layer (MML) of Tetrabutylammonium chloride (TBAC) was introduced, which can self-assemble onto the surface of perovskite by means of a facile solution method. TBAC MML possesses a strong interface dipole pointing outward of the surface of perovskite, which promotes the built-in electric field and reduces the contact barrier for hole extraction. Accordingly, the carrier extraction rate and recombination resistance are enhanced by 1.5 and 4 times, respectively. PSCs treated by TBAC (TBAC-PSCs) induced a champion efficiency of 23.50% with fill factor (FF) of over 82%. In addition, TBAC MML can prevent the adsorption of H 2 O and O 2 onto the surface of perovskite, and thereby enhance the stability of PSCs. After being aged in ambient air for 1000 h, TBAC-PSCs sustained the initial efficiency of over 90% which is only 58% for the control devices. [ABSTRACT FROM AUTHOR]

• Solution processed C 60 films enabled perovskite solar cell efficiency to over 20% • Super-hydrophobic C 60 films promoted the air-stability of perovskite solar cells. • The key for high quality solution processed C 60 films was elucidated. Solution processed fullerene (C 60) films as the electron transport layers (ETLs) promise to substantially reduce the cost of the perovskite solar cells (PSCs). However, the self-aggregation nature of C 60 when dissolved in a solvent with high solubility (e.g., o-dichlorobenzene, o-DCB) makes the efficiency of the resulting PSCs lower than 18%. In this paper, we proposed a novel recipe of C 60 precursor solutions (XP-C 60) by using o-xylene (o-X) as the solvent and PCBM solution in chlorobenzene (CB) as the additive, which can simultaneously inhibit the aggregation of C 60 and advocate fast solvent drying. Homogeneous C 60 films of high quality from the new recipe solution can be readily fabricated at room temperatures, advocating the efficiency of the printed PSCs to over 17%. Finally, a champion efficiency of over 20% for the PSCs was achieved which is comparable to that of the PSCs with PCBM as the ETLs. XP-C 60 based PSCs also show good stability, which sustain 85% of its initial efficiency as being exposed in air with a relative humidity (RH) of 50% for over 20 days. Our work helps to understand the film-formation dynamics of C 60 by a solution method and cut the production cost of the PSCs to the bone. [ABSTRACT FROM AUTHOR]

[Display omitted] • Stabilize SnO 2 colloids with EDTA-2M (M represents K, Rb or Cs). • Improve the electrical and surface properties of the SnO 2 films with EDTA-2M. • Promote the quality of the perovskite films with EDTA-2M. • The 1.57 eV bandgap PSCs realized a champion efficiency of 23.30% (V OC = 1.171V). • The 1.69eV bandgap PSCs reached an efficiency of 19.76% (V OC = 1.266V). The electron transport layer (ETL) is of great importance for preparing high-efficiency perovskite solar cells (PSCs). Here we introduced EDTA-2 M (M represents K, Rb or Cs) molecules to stabilize SnO 2 colloids, and improve the electrical and surface properties of the SnO 2 films. With the help of EDTA-2 M, the electron mobility of SnO 2 -based perovskite films is increased from 3.6 × 10-4 to 1.27 × 10-3 cm2V-1s−1. In addition, EDTA-2 M molecules can effectively passivate the interface defects of SnO 2 and promote the quality of the perovskite films. All the improvements suppress the carrier recombination, leading to a smaller open circuit voltage (V OC) loss. Finally, the 1.57 eV bandgap PSCs based on EDTA-2 M modified SnO 2 realized a champion efficiency of 23.30% (V OC = 1.171 V) with a negligible hysteresis, while the 1.69 eV bandgap perovskite device reached an efficiency of 19.76% (V OC = 1.266 V). The unencapsulated PSCs based on EDTA-2 M modified SnO 2 only drop 5% of the initial efficiency after being exposed to the ambient atmosphere for 1200 h. [ABSTRACT FROM AUTHOR]

Eliminating the carrier recombination loss is of great significance for the performance of the perovskite solar cells. Here, three small molecules with the same core unit (ITIC) but different end groups (nominally IT-M and IT-4F) were incorporated into the perovskite films by engineering the composition of the perovskite precursor solutions. It is suggested that the molecules not only increase the grain size and passivate the non-coordinated Pb2+ cations among the grain boundaries, but also balance the carrier transport by regulating the electronic structure of the perovskite/molecule hybrid films (PMHFs), and produce a hydrophobic surface to prohibit the moisture permeation into the active layers. Finally, the devices based on PMHFs exhibits a significant improvement in photoelectric conversion efficiency (PCE) and the stability. The PSCs based on IT-4F realizes a champion PCE of 19.75% (reverse sweep up to 20.08%), which is far larger than those control ones (16.65%). Cells sustain over 90% of their initial efficiency after 20 days in a N 2 -filled glove box. Image 1 • Small molecules are introduced into perovskite precursor solution. • Interface defects are suppressed. • The electrons and holes give rise to a more balanced transporting behavior. • PSCs have improved stability. [ABSTRACT FROM AUTHOR]